CN106479476A - A kind of clean fracturing fluid and preparation method thereof - Google Patents

Abstract

The invention provides a kind of clean fracturing fluid and preparation method thereof, by weight percentage, this fracturing fluid includes long-chain two polyamides propyl group amine oxide 0.1% 5%, anion-polyacrylamide polymer containing hydrophobic group 0.1% 0.6%, salt 0 4%, balance of water, clean fracturing fluid can be applied in oil-gas field fracturing, it can be obtained by higher denseness and viscoelasticity under relatively low concentration, obtains more preferable rheological characteristic and sand carrying effect.

Description

A kind of clean fracturing fluid and preparation method thereof

technical field

The invention belongs to the field of oil and gas development, and in particular relates to a clean fracturing fluid and a preparation method thereof.

Background technique

my country's oil and gas fields are rich in reserves in low-permeability layers, but their natural productivity is low or has no natural productivity at all. It is difficult to obtain economic development value without fracturing and stimulation to improve single well production. The application of fracturing fluid technology to develop such reservoirs is of great significance. The main function of fracturing fluid is to bring viscoelastic fluid and proppant into the fractured formation to increase permeability to increase oil and gas production.

The amount of residue after hydration of the fracturing fluid directly affects the fracturing effect. Commonly used fracturing fluids are high-molecular-weight guaran or its modified products, and the residue content of such fracturing fluids is still relatively high. The residues come from the insoluble matter of the natural polymer itself and the incomplete gel-broken products after cross-linking with metals. These residues will cause irreparable damage to the permeability of the propped zone of the fracturing fracture and the permeability of the formation, seriously affecting the fracturing process. The effect of increasing production.

Hydrophobic polymers can form molecular aggregates through intermolecular non-covalent bond interactions and associations. As synthetic polymers, they have no residue and little damage to the formation. Viscoelastic surfactants are also the result of association and aggregation of small molecules. They are applied to fracturing fluids in oil and gas fields. After encountering oil, the aggregation state changes and becomes a spherical low-viscosity liquid, which automatically breaks the gel. Because it is a small molecule and has no residue, Little damage to the formation; viscoelastic surfactant fracturing fluid is easy to construct on site, does not require too much equipment, cross-linking agent, gel breaker and other additives, so it has its unique advantages.

U.S. Patent 5,551,516 discloses a viscoelastic surfactant-based fracturing fluid in which water-soluble inorganic salts such as potassium chloride or ammonium chloride and similar water are used together with cationic surfactants. Organic salts of sodium sylate or alcohols as stabilizers. US Patent Nos. 5,964,295, 6,435,277, and 6,412,561 disclose composition types and methods of use of viscoelastic surfactant-based fracturing fluids. US Patent No. 6,703,352 discloses a composite composition of a single-chain amphoteric surfactant with a carbon chain length of 12-24, inorganic salts, and organic salts.

CN1285700C discloses a formula for cleaning fracturing fluid, which is mixed with unsaturated fatty acid salt with 18 carbon atoms and brine or with fatty acid with 18 carbon atoms, inorganic base and brine. CN1752173A discloses a clean fracturing fluid additive, which consists of long carbon chain alkyl quaternary ammonium salt, long carbon chain alkyl dimethyl amine oxide, salicylate, glycol ether, low carbon alcohol and water. CN101775276A discloses a method for preparing a fracturing fluid that can be used at relatively high formation temperatures, which includes Gemini cationic surfactants, amphoteric surfactants, electrolyte salts, counter ion salts, cosolvents, water, and the like. CN102181279A discloses a cationic quaternary ammonium salt type surfactant fracturing fluid with multiple hydrophilic groups.

Although viscoelastic surfactant-based fracturing fluid has many advantages such as no residue and less damage to the formation, its high concentration and corresponding high cost require further improvement.

Contents of the invention

In order to solve the above technical problems, the object of the present invention is to provide a clean fracturing fluid and its preparation method, the fracturing fluid can obtain higher consistency and viscoelasticity at a lower concentration, and has better rheological properties and sand carrying effect.

In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is, a kind of clean fracturing fluid, by weight percentage, this fracturing fluid comprises dipolyamidopropyl amine oxide surfactant 0.1%-2%, contains hydrophobic group 0.1%-0.6% of anionic polymer, 0-4% of salt, and the balance is water; the anionic polymer containing a hydrophobic group is a water-soluble polymer containing a sulfonate and a hydrophobic group; the dimer Acyl propyl amine oxide surfactant has the molecular structure shown in following formula I

In formula I,

R ₁ is an acyl group whose carbon number is C36 and contains 2 -CO- groups;

R ₂ is a methylene group whose carbon number is C2-5;

R ₃ is an alkyl group whose carbon number is C1-4, or -CH ₂ CH ₂ OH;

R ₄ is an alkyl group whose carbon number is C1-4, or -CH ₂ CH ₂ OH;

The R has _a structure as shown in any one of the following formula II or formula III:

The dipolyamide amine oxide surfactant includes one or a combination of formula II and formula III; the dipolyamide amine oxide surfactant contains two hydrophilic groups in its molecular structure And two hydrophobic groups, the carbon number of the hydrophobic groups is 36, and contains two -CO-acyl groups, its specific structure is:

The anionic polymer containing hydrophobic groups is polyacrylamide, polyacrylamide includes hydrophobic groups and anionic groups, and its molecular weight is 500,000-3 million; the hydrophobic groups include straight chains with carbon numbers of C12-22 Or a branched hydrocarbon chain group, the hydrophobic group is connected to the main chain through an amide bond or an ester bond, and the anion group is a carboxyl group or a sulfo group.

The molecular weight of the polyacrylamide is 500,000-2,000,000, and the molecular weight of the hydrophobic group accounts for 0.5-2% of the molecular weight of the entire polyacrylamide in molar ratio.

The salt includes one or a combination of potassium chloride, ammonium chloride, and quaternary ammonium salts.

By weight percentage, it also includes 0-2% other surfactants, said other surfactants are one or more of anionic surfactants, cationic surfactants, nonionic surfactants and alcohol solvents combination, the addition of the alcohol solvent is 0-1%;

The anionic surfactants include alkylsulfonate surfactants or sulfate surfactants;

Described cationic surfactant comprises alkyl quaternary ammonium salt surfactant;

The nonionic surfactant comprises one or more combinations of alkyl fatty alcohol polyoxyethylene ether, alkyl glucoside, and alkyl amide;

The alcohol solvent includes one or a combination of methanol, ethanol, isopropanol, ethylene glycol, and propylene glycol.

A method for preparing a clean fracturing fluid, comprising the following steps: mixing a dipolyamidopropylamine oxide surfactant and a salt, adding it to an aqueous solution of an anionic polymer containing a hydrophobic group, and stirring evenly to obtain a clean fracturing fluid liquid.

The preparation method of described dipolyacylpropyl amine oxide surfactant comprises the following steps:

Reaction of dimerized fatty acid and organic amine at 160-180°C until the acid value of the reaction system is less than 6, and the reaction is completed to obtain the first reaction intermediate, wherein the molar ratio of dimerized fatty acid to organic amine is 1:2;

Distilling off the water and the remaining organic amine in the first reaction intermediate to obtain the second reaction intermediate;

The second reaction intermediate is reacted with hydrogen peroxide aqueous solution at 60-80° C. for 4-6 hours to obtain dipolyamidopropylamine oxide surfactant.

The dimer fatty acid is dimer octadecanoic acid; the organic amine is N,N-dimethyl-1,3-propanediamine.

The present invention also provides the application of the above-mentioned clean fracturing fluid in oil and gas field fracturing, which can be applied with reference to the application methods of other fracturing fluids in the prior art.

The cleaning fracturing fluid provided by the present invention has the following beneficial effects: the present invention uses dipolyamide amine oxide type surfactants and hydrophobic polymers to greatly increase the viscosity, and has better compatibility with various ions. Therefore, it is different from traditional Compared with the surfactant fracturing fluid, the fracturing fluid provided by the present invention can obtain higher consistency and viscoelasticity at a lower concentration, obtain better rheology and sand-carrying effect, and be compatible with various ions Sex is better.

Further, in the present invention, salt is added, and the salt includes one or a combination of potassium chloride, ammonium chloride, and quaternary ammonium salt. Adding salt can prevent the clay from swelling.

Furthermore, the present invention adjusts the dissolution rate of the fracturing fluid and improves its ability to resist shearing by adding nonionic surfactants and cationic surfactants into the fracturing fluid.

detailed description

In order to have a clearer understanding of the technical features, purpose and beneficial effects of the present invention, the technical solution of the present invention is described in detail below, but it should not be construed as limiting the scope of the present invention.

Example 1

The present embodiment provides a kind of preparation method of cleaning fracturing fluid, and it comprises the following steps:

1) Synthesis of Dipolyoctadecylamide

Take 100 g of high-purity dimer acid (dimer octadecanoic acid with a carbon number of C36>95%) and add it to N,N-dimethyl-1,3-propylenediamine (38.3 g, 0.38 mol), After mixing evenly, heat to 160-180°C, keep it warm for 3-8 hours, distill off the water generated by the reaction, and the reaction ends when the acid value is less than 6; distill to remove excess N,N-dimethyl-1,3-propane Diamine, to obtain high-purity dimer octadecylamide.

2) Synthesis of Dipolyamidopropylamine Oxide Surfactant

Add 10.3 g of 30% concentration of hydrogen peroxide into 27 mL of water and 12 g of dipropylene glycol, mix and heat to 70-80° C., then add 20 g of high-purity dioctadecylamide obtained in step 1), at 60-80 Reaction at ℃, when the reaction process reaches 98% of the theoretical value through chromatographic monitoring, the reaction is complete. In this embodiment, the reaction time is 4-6 hours, and the effective concentration is 26% of the product of active content, i.e. dipolyamide Amine oxide surfactant; Final product structure is the homologue shown in formula IV or V:

3) Preparation of supramolecular clean fracturing fluid

The components and codes are as follows:

HMPAM: Hydrophobic modified polyacrylamide, that is, anionic partially hydrolyzed polyacrylamide containing a hydrophobic group, the carbon number of the hydrophobic group is C18, and the hydrophobic group is connected to the main chain through an amide; the molecular weight is 2 million;

DIAMO: dipolyamide amine oxide surfactant (amide structure IV, V): the carbon number of the polyacyl group R ₁ is C36.

AMO: single chain C18 amide amine oxide surfactant.

The preparation process is as follows: after fully dissolving HMPAM, under stirring conditions, add one or a combination of DIAMO in the ratio shown in Table 1 to form different series of uniform liquid systems.

Example 2

In this example, on a Haake RS6000 rheometer, the viscosities of liquids with different compositions were tested at a shear rate of 100 s ⁻¹ at 70° C., and the results are shown in Table 1 (concentrations are weight ratios to effective substance content).

Table 1 Viscosity test results

It can be seen from Table 1 that in different series of homogeneous liquids, the viscosity obtained after compounding the dipolyamide-containing amine oxide surfactant and the anionic polymer containing a hydrophobic group is higher than the viscosity when the two are used alone times, higher than single-chain amine oxide.

Example 3

In this embodiment, the dynamic viscoelasticity of the composite sample containing HMPAM and surfactant in Example 2 was tested on a Haake Mars rheometer, and the results are shown in Table 2.

Table 2 Viscoelastic properties (60°C, 0.01rad/s)

Composition, by weight percent G' (storage modulus), Pa G” (loss modulus), Pa 0.25%HMPAM+0.2%DIAMO 0.52 0.21

It can be seen from Table 2 that when the frequency of the composite sample is very low (0.1rad/s), G' (storage modulus) is greater than G" (loss modulus), indicating that it has high viscoelastic properties. The sand-carrying performance is favorable.

Example 4

In this example, the supramolecular cleaning fracturing fluid provided by the present invention is further tested for residue content, referring to SY/T5107-1995 water-based fracturing fluid performance evaluation method 6.6 Determination of fracturing fluid residue content, and the results are shown in Table 3.

Table 3 residue content

serial number Composition (by weight percentage) Residue content (mg/L) 1 0.25%HMPAM+0.2%DIAMO 0 2 0.25% guar gum jelly 280

It can be seen from Table 3 that the supramolecular clean fracturing fluid provided by the present invention has no insoluble residues and belongs to clean fracturing fluid. And traditional 0.25% guar gum jelly residue is higher.

Claims (10)

1. A clean fracturing fluid, characterized in that, in weight percent, the fracturing fluid comprises 0.1%-2% of a dipolyamide oxide surfactant, and 0.1%-2% of an anionic polymer containing a hydrophobic group 0.6%, salt 0-4%, and the balance is water; the anionic polymer containing hydrophobic groups is a water-soluble polymer containing sulfonate and hydrophobic groups; The agent has a molecular structure as shown in the following formula I In formula I, R ₁ is an acyl group whose carbon number is C36 and contains 2 -CO- groups; R ₂ is a methylene group whose carbon number is C2-5; R ₃ is an alkyl group whose carbon number is C1-4, or -CH ₂ CH ₂ OH; R ₄ is an alkyl group whose carbon number is C1-4, or -CH ₂ CH ₂ OH. 2. clean fracturing fluid according to claim 1, is characterized in that, described R has the structure shown in any _one of following formula II or formula III: 3. Clean fracturing fluid according to claim 2, is characterized in that, described dipolyacylpropyl amine oxide surfactant comprises the combination of one or two in formula II, formula III; Amide amine oxide surfactant, its molecular structure contains two hydrophilic groups and two hydrophobic groups, the carbon number of the hydrophobic groups is 36, and contains two -CO-acyl groups, its specific structure is: 4. The cleaning fracturing fluid according to claim 1, characterized in that, the anionic polymer containing hydrophobic groups is polyacrylamide, and polyacrylamide includes hydrophobic groups and anionic groups, and its molecular weight is 50- 3 million; the hydrophobic group includes a straight chain or branched hydrocarbon chain group with a carbon number of C12-22, the hydrophobic group is connected to the main chain through an amide bond or an ester bond, and the anionic group is carboxyl or sulfo. 5. The cleaning fracturing fluid according to claim 4, characterized in that, the molecular weight of the polyacrylamide is 50-2 million, and the molecular weight of its hydrophobic group accounts for 0.5-2% of the molecular weight of the entire polyacrylamide by molar ratio. %. 6. The clean fracturing fluid according to claim 1, characterized in that the salt comprises one or a combination of potassium chloride, ammonium chloride, and quaternary ammonium salts. 7. The cleaning fracturing fluid according to claim 1, characterized in that, by weight percentage, it also includes other surfactants of 0-2%, and said other surfactants are anionic surfactants, cationic surfactants One or more combinations of surfactants, nonionic surfactants and alcoholic solvents, the addition of the alcoholic solvents is 0-1%; The anionic surfactants include alkylsulfonate surfactants or sulfate surfactants; Described cationic surfactant comprises alkyl quaternary ammonium salt surfactant; The nonionic surfactant comprises one or more combinations of alkyl fatty alcohol polyoxyethylene ether, alkyl glucoside, and alkyl amide; The alcohol solvent includes one or a combination of methanol, ethanol, isopropanol, ethylene glycol, and propylene glycol. 8. A method for preparing the cleaning fracturing fluid described in any one of claims 1-7, is characterized in that, comprises the following steps: after dipolyamidopropylamine oxide surfactant and salt are mixed, add to containing The aqueous solution of the anionic polymer with a hydrophobic base is stirred evenly to obtain a clean fracturing fluid. 9. method according to claim 8, is characterized in that, the preparation method of described dipolyamidopropyl amine oxide surfactant comprises the following steps: Reaction of dimerized fatty acid and organic amine at 160-180°C until the acid value of the reaction system is less than 6, and the reaction is completed to obtain the first reaction intermediate, wherein the molar ratio of dimerized fatty acid to organic amine is 1:2; Distilling off the water and the remaining organic amine in the first reaction intermediate to obtain the second reaction intermediate; The second reaction intermediate is reacted with hydrogen peroxide aqueous solution at 60-80° C. for 4-6 hours to obtain dipolyamidopropylamine oxide surfactant. 10. The method according to claim 9, characterized in that, the dimer fatty acid is dimer octadecanoic acid; the organic amine is N,N-dimethyl-1,3-propanediamine.